Madison - The American Civil Liberties Union sued the State of Wisconsin on Tuesday over a new law requiring voters to show government-issued photo identification, charging that the measure violates the U.S. Constitution.

The lawsuit says that the state is infringing on some citizens' right to vote and to be treated equally under the law and amounts to a kind of poll tax on voters who lack the documents needed to get an approved ID.

Republican lawmakers and Gov. Scott Walker, who is named in the lawsuit along with a long list of other state officials, have said they believe the measure will withstand a court challenge.

The action came Tuesday ahead of a scheduled speech by U.S. Attorney General Eric Holder in which he vowed to enforce civil rights protections amid a flurry of voter ID laws recently passed around the country. The Wisconsin lawsuit was filed in federal court in Milwaukee by the national ACLU and its Wisconsin affiliate and the National Law Center on Homelessness & Poverty on behalf of a group of senior citizens, minorities and homeless residents.

"This lawsuit is the opening act in what will be a long struggle to undo the damage done to the right to vote by strict photo ID laws and other voter suppression measures," said Jon Sherman, an attorney with the ACLU Voting Rights Project.

Critics of the photo ID law say that there are no cases of voter impersonation and that the law will make it harder for vulnerable groups to vote. Proponents argue the measure will discourage voter fraud and give the public more faith in elections.

Walker spokesman Cullen Werwie noted that at least 15 other states have enacted some photo ID requirement and that photo ID has been upheld by the U.S. Supreme Court.

"The common sense election reforms signed into law earlier this year by Governor Walker are constitutional," Werwie said in an email. "Requiring photo identification to vote helps ensure the integrity of our elections - we already require it to get a library card, cold medicine, and public assistance."

Dana Brueck, a spokeswoman for the state Department of Justice, said the state would review the lawsuit and file its response within the required time.

"The allegations in this lawsuit are nothing new, and we are confident that the voter ID law will be upheld," Brueck said in an email.

In October, the League of Women Voters of Wisconsin filed its own challenge to the new law under the state constitution in Dane County Circuit Court. The lawsuits come as groups moved forward with petition drives to recall Walker and state senators.

The suits could determine whether the photo ID requirement is in place for any recall elections, as well as the fall 2012 presidential election.

Ed Fallone, a Marquette University law professor who has blogged about the issue, noted that in a 2008 case, Crawford v. Marion County Election Board, the U.S. Supreme Court had upheld Indiana's photo ID law but left open a possibility that such laws might be successfully challenged if they were unfairly applied.

Fallone said that he doubted Wisconsin's entire law would be struck down but that the lawsuit might succeed at least in part if statistics can show larger numbers of people would be affected.

Karyn Rotker, the senior staff attorney for the ACLU in Wisconsin, said her group was seeking that information.

Different IDs qualify

To vote, Wisconsin residents will be required to show a driver's license, state-issued ID card, military ID, passport, tribal ID, college ID or naturalization certificate. To keep the law from being a poll tax, the measure requires the state Division of Motor Vehicles to waive the normal $28 fee for state IDs for people who seek them for the purpose of voting.

But the ACLU suit notes that to get a free state ID, voters must present the DMV with a birth certificate, passport or other documentation. Birth certificates cost $20 in Wisconsin, and there are also fees for the other types of documentation as well.

The lawsuit lays out the case of Ruthelle Frank of Brokaw who serves on her village board and has voted religiously since 1948. Frank, 84, has never had a birth certificate, the lawsuit says.

The state has a record of Frank's birth, which would allow her to have a birth certificate made. But her maiden name is misspelled in those records, meaning Frank could have to pay extra to have it corrected.

The lawsuit also lays out of the case of Barbara Oden, a 57-year-old resident of Milwaukee who has no photo ID, birth certificate or Social Security card. The lawsuit says that Oden has no income or savings and was denied a Social Security card because she doesn't have a photo ID.

The Government Accountability Board, which is tasked with overseeing state elections, plans to launch a television and radio ad campaign on the new law Jan. 2. Some of the ads will remind people to bring their IDs to the polls, while others will tell those who don't have IDs how they can get them, according to rough cuts of radio ads played at the board's meeting Tuesday.

The "Bring it to the Ballot" ads direct people to the website, where they can learn more about what IDs can be used for voting and how to get a free state-issued ID.

Patrick Marley of the Journal Sentinel staff contributed to this article.

About Jason Stein

Jason Stein covers the state Capitol and is the author with his colleague Patrick Marley of "More than They Bargained For: Scott Walker, Unions and the Fight for Wisconsin." His work has been recognized by journalism groups such as the American Society of News Editors, the Society of American Business Editors and Writers, and the Association of Capitol Reporters and Editors.